Cell cycle 2

What is the role of B-CDK1 in G2?

As G2 progresses more cyclin B produced

forms B-CDK1

regulates progression In mitosis

What is the appearance of DNA at the end of G2?

two identical sister chromatids held by centromere to form chromosome

What is the G2/M checkpoint?

cell checks duplicated DNA for damage and repairs before mitosis

What is mitosis divided into?

Prophase

Prometaphase

Metaphase

Anaphase

Telophase

Cytokinesis

What occurs during the prophase?

Chromatin condensed to chromosomes

Chromosomes are visible

Mitotic spindle form

What role does B-CDK1 play in prophase?

activates condensin and SL1

Promotes chromosome condensation

What occurs during the prometaphase?

Nuclear membrane disappears

Chromosomes attached to microtubules from centrosome (proteins that organise microtubules)

attach to centromere by kinetochore

What role does B-CDK1 have in prometaphase?

Phosphorylates Lamin causing break down of nuclear membrane

What occurs during the metaphase?

Chromosomes pulled by microtubules and line up on metaphase plate

What role does B-CDK1 have in metaphase?

phosphorylates seperase which is involved in separating sister chromatids causing securin to bind deactivating it

and anaphase promoting complex (APC) which targets proteins for breakdown

What is the role of the metaphase checkpoint?

Ensures chromosomes are in correct positions and attached to mitotic spindle

What occurs during anaphase?

chromatids separate and pulled to poles

Microtubules shorten via depolymerisation

What occurs to cyclin-b in anaphase?

proteolysed via APC

Seperase activated and chromatids can split

CDC14b activated which acts as phosphatase

What happens during the telophase?

chromosomes at opposite poles and decondense

nuclear envelope reforms

microtubules dissolve

What does CDC14b do?

dephosphorylates lamins, SL1, Rb

Mitogen needed to start cell cycle again

resets cell cycle

What occurs during cytokinesis?

Cytoplasm divides

Contractile ring has F-actin and myosin

myosin moves along f-actin, membrane constriction

cell is cleaved into two